Muffler assembly



June 10, 1958 ss T AL 2,838,129

MUFFLER ASSEMBLY Filed Aug. 18, 1955 2 Sheets-Sheet 1 rzza #3666 p658?Ma. 520,

June 1 1958 A. HESSE ET AL MUFFLER ASSEMBLY 2 Sheets-Sheet 2 Filed Aug.18, 1955 Jazz/e z-zifs C rz-za Hesse Pier Ma zfzaf United States PatentMUFFLER ASSEMBLY Arno Hesse and Peter Walzak, Chicago, 111., assignorsto Mail Tool Company, Chicago, 111., a corporation of Illinois Thisinvention relates to a manifold system for internal combustion enginesand more particularly to a muffler assembly on a two cycle gasolineengine.

Two cycle gasoline engines of the spark ignition type with crankcasescavenging, one of the simplest prime movers known, require no separateinlet or exhaust valve systems as ports opened and closed by the pistonin its reciprocation inthe cylinder are provided to admit the fuelmixture and exhaust the burned gases. Vaporized fuel is passed from thecarburetor directly into a sealed crankcase and the downstroke of thepiston is utilized to compress the mixture of fuel and air. A lay-passor transfer port allows the fuel mixture into the combustion chamber.This engine scavenges by virtue of a pressure difference between thetransfer and exhaust ports. During each cycle the exhaust port is openeda few degrees before the transfer port in order to reduce the pressurein the cylinder to a low value before scavenging starts so that theburned gases may be swept out the exhaust port in front of the incomingwave of vaporized fuel mixture from the crankcase. improved scavengingresults when the dynamics of the system is such that the exhaust gasesflow out the restricted orifice of the exhaust port in an efficientmanner in front of the denser fuel air mixture entering the combustionchamber from the transfer port.

It is apparent that. scavenging will be considerably affected by backpressure built up in the exhaust passage. Accordingly, mufflers and longexhaust passages which have an undesirable effect on scavenging byreason of the build up of back pressure are to be avoided.

Another factor affecting engine performance relates to mechanicallosses, a very large portion of which arises from the friction of. thepiston and rings. This is attributable to the large area of the surfacesin contact, the high velocities between the surfaces,-and from the factthat lubrication conditions are relativelypcor.

In order to keep engine friction within reasonable limits it isdesirable to use oils with the lowest viscosity possible withoutencountering excessive ring and cylinder wear or excessive oilconsumption. In two cycle engines where piston loads and temperaturesare not high, satisfactory lubrication of the piston and rings may behad with a low viscosity lubricant. Therefore, in two cycle engines withcrankcase scavenging it has been common practice to mix a smallproportion of low viscosity oil with the fuel to lubricate the pistonsand rings.

With this method of lubrication oil vapor is passed with the vaporizedfuel into the crankcase to secure an oil film deposit on the cylinderwalls for lubrication purposes, and the oil vapor which passes into thecombustion chamber with the vaporized fuel is either burned completelyvand blown as a gas out the exhaust passage or burned incompletely anddeposited as carbon on the Walls of the cylinder or in the exhaustpassage or port.

During the firing of any engine the oil on the cylinder walls is exposedto extremely high temperatures and a certain part of this oil ignites,is burned and passes out the exhaust. This incomplete burning leavesparticles of carbon and gum deposits on the cylinder walls and isencountered in the operation of both conventional four cycle engines andtwo cycle engines. Engines running at high temperatures may burn awaysome of the carbon which tends to deposit on the cylinder walls, but thebuilding up of carbonaceous deposits in the exhaust passage, blockingthe exhaust port, and in the ring grooves (piston ring gumming) cannotbe entirely prevented. In addition to this condition, however, anexcessive build up of carbon deposits in the cylinder resulting inchoking the exhaust port is a major problem with two cycle engines whichhave piston and piston ring lubrication by oil mixed with the fuel.

Another effect of mixing oil with the fuel is that the higher viscosityoil holds in suspension larger particles of grit or foreign matter thanwould be held in suspension in the lower viscosity gasoline. Suchmaterial in suspension in the fuel and passing into the combustionchamber may cause additional deposits on the cylinder walls, spark plugsand head of the piston and also may, incidentally, promote corrosion ofthese parts.

This invention is used in connection wih the exhaust system of a twocycle engine which utilizes crankcase scavenging and which is adapted topermit piston cylinder lubrication by oil mixed with the fuel.

A large exhaust port is required for proper scavenging and improvedengine performance by reducing the time of the blow-down process. Thisexhaust port is usually located in the wall of the cylinder adjacent thebase and in the flow of air passing over the engine so that exhaustgases may be carried away from the end of the exhaust pipe and to permitproper cooling.

it is an object of this invention to provide such an exhaust system withan extremely short exhaust pipe and also to provide a muflier arrangedon the end of the exhaust pipe so constructed as to minimize the effectof back pressure build up.

Since the accumulation of carbon and also the deposit of solid particlesor of gumming carbonaceous deposits in the exhaust passage decreases thearea of the passage, there results a tendency to choke the passagethereby affecting back pressure of the exhaust and decreasing scavengingefiiciency. In addition any choking of the exhaust port affectsdetrimentally the dynamics of the system with a corresponding reductionin scavenging efliciency. This is very noticeable in the operation of'two cycle engines which are particularly sensitive to this condition byreason of the burning in the combustion chamber of oil vapor during eachcycle of engine operation.

It is desirable in the maintenance of such engines that this carbondeposit, as well as the deposit of gum and solid particles, be r movedperiodically and conventional practice is to disassemble the engine,remove the piston, and scrape the exhaust passages with a blunt tool.Periodic overhauling for proper maintenance also includes the scrapingof the cylinder walls and the head of the piston to remove accumulationsof foreign material.

It is very noticeable when the exhaust port of a two cycle engine beginsto choke with carbon because the engine loses much of its normal power.On most engines it is possible but only with considerable difficulty, toloosen the bolts connecting the exhaust system to the cylinder head andremove the exhaust pipe so as to permit cleaniru of the exhaust portwalls and of the exhaust pipe itself.

Therefore, this invention has as a further object the provision of amanifold assembly which enables the operator to conveniently and quicklygain access to the exhaust ports for cleaning purposes. Moreparticularly it is an object of this invention to provide in combinationwith the exhaust port flange of a two cycle engine, an

In accordance with our invention we provide an adapter plate which isbolted to the exhaust port flange and which is provided with an exhaustpassage communicating with the exhaust port. The outer rim of the plateis provided with a seat to receive the muffler and arrangedcooperatively on the mufller and on the plate there is a clip forsecurely fastening the mufller to the plate.

Further in accordance with this invention the mufiier is constructed ofa chamber with outlet openings in one wall and with another wallarranged as a bafiie positioned transversely to the axis of the exhaustpassage at an angle to deflect the gases into the chamber around whichthe gases swirl prior to exit through the openings.

Further objects will become apparent from the following descriptiontaken in connection with the accompanying drawings wherein: 1

Fig. 1 is a view in elevation of the muflier of this invention mountedon a two cycle engine cylinder;

Fig. 2 is a view in section of the mufller and cylinder taken on lines22 of Fig. 1; r

Fig. 3 is a detail sectional view taken on lines 3-3 of Fig. 1;

Fig. 4 is a section taken on lines 4-4 of Fig. 2, showing the mufflerassembly from the rear;

Fig. 5 is an exploded view of the muflier and mounting plate.

The mufiler shown in Figs. 1 through 5 is supported on a cylindercasting of a two cycle engine which has all functional parts including apiston 11, connecting rod 12, and spark plug 13. The cylinder casting 10is provided with fins 14 for cooling, and has a combustion chamber 15which communicates to atmosphere through exhaust port 16 and to thecrank case through by-pass port 17. To provide a support for a mutflerassembly, the cylinder casting 10 has an exhaust flange 18 substantiallyrectangular in form and with threaded openings to receive bolts formounting the mufiier assembly in place.

The muflier of this invention comprises a plate 22 adapted to be mountedon the exhaust port flange 18 by means of bolts 19, 20. The plate 22 isconstructed of a substantially fiat stamped piece with an offset portion23 forming a bracket and provided with openings 24, 25 through which thebolts pass to secure the plate on the cylinder casting. In the offsetportion 23 there is an opening 26 which registers or communicates withthe exhaust port 16 to receive the exhaust gases from the combustionchamber of the cylinder.

Opposite sides 27, 28 of the plate 22 are arranged substantiallyparallel and are bent back over the top of the plate to make a narrowlip 29, 30. To securely fasten the plate 22 to the cylinder casting alug 35 is riveted on the lower end of the plate which lug has an opening36 receiving a bolt 37 which is threaded into the cylinder casting.

' Mounted on the plate 22 is the dished mufller cover 21 which formswith the plate 22 the muffler cavity. The muflier cover 21 is shaped tocorrespond generally in outward dimensions with the plate 22 and has anouter Wall 40 opposite opening 26 in the plate arranged obliquely tosaid opening so as to deflect gases entering the muffler cavity. Thelower side 41 of the muffler cover lies against a rim 42 standing atright angles to the plate 22 sealing the muflier cavity against leakage.The rim 42 extends partially along one side 43 of the plate and thecorresponding side wall of the muffler cover 21 extends substantially atright angles to the plate to fit against the rim.

To enable the cover 21 to be mounted on plate22, along opposite sidesthere are formed flanges 45, 46 which slip beneath the lips 29, 34 onthe plate. On the upper side of the muffler cover 21 and extendingpartially around one side is a head 47 lying under the edge of the plate22. The bead abuts against the underside of the plate and ,4 forms aseal preventing the escape of exhaust gases from the muflier cavity.

a a In the upper sloping portion of the outer wall of the mufller cover21 there are provided a plurality of parallel slots 50 with louvers 51angularly arranged to deflect the exhaust gases emitted from the slots.

Also fastened on the underside of the plate 22 is a spring clip 53 whichserves to retain the muffler cover in place seated on the plate. Thespring clip 53 is fastened by means of rivets 54 and may be bent awayfrom the plate by applying pressure against the arm 55.

In the exploded view of Fig 5 mufiler cover 21 is shown slid away fromplate 22. It may readily be observed that the lips 29, 30 on the plateare arranged to fit over the flanges 45, 46 on the muffler cover andsecurely lock the muflier cover in place to form the muflder cavity. Therim 42 at the lower end of the plate 22 which extends partially aroundone side 43 of the plate serves the function of sealing the mufilercavity by snugly fitting against the companion side walls of the coverand also seats the cover as it is slid into place on the plate.

An important feature of the present invention resides in the fact thatthe muffler cover 21 may be quickly removed from the plate 22, providingeasy access to the exhaust port 16. In the maintenance of two cycleengines it is frequently necessary to clean this exhaust port and alsoto scrape carbon from the top of piston 11 and around the lower end ofspark plug 13. After removing the cover 21 a tool may be inserted forscraping the exhaust port 16 which may also be manipulated to scrape thetop of the piston 11 and portions of the combustion chamber which haveaccumulated carbon deposits. The mufiler cover can then be slid backinto place on the plate and is permanently mounted without danger ofbecoming loosened from engine vibration or as a result of beingaccidently jarred.

The exhaust gases from the exhaust port 16 are deflected by theobliquely arranged outer wall 40 and whirlacross the mufller cavity tobe forced through the slots and past the louvers in the mufiier cover.The louvers may be arranged to deflect the gases in any desireddirection without materially affecting the performance characteristicsof the muffler.

Particular attention is directed to the fact the mufller cavity is ofsubstantial size, as is the exhaust port 16, to reduce back pressure soas not to unduly affect the dynamics of the exhaust system.

The invention has been described with reference to particular preferredembodiments and it is understood the details are merely illustrative andthat the invention may be carried out in other ways without departingfrom the true spirit and scope of the appended claims.

We claim: e e

1. A muffler for the exhaust port of a cylinder of an internalcombustion engine, said cylinder being provided with an exhaust portflange, comprising a plate carried on the engine cylinder, said platehaving an offset portion forming a bracket for mounting the plate on theexhaust port flange, with an opening in said portion communicating withthe exhaust port, said plate having substantially parallel sides bentover to provide parallel lips, and a dished muffler cover adapted to besupported on the plate to form a muffler cavity, having substantiallyparallel sides formed with narrow flanges to slip under the lips of theplate and slidably fasten the cover thereto, whereby the cover may beremoved providing easy access to the exhaust port.

2. A muffler for the exhaust port of the cylinder of an internalcombustion engine, comprising a plate mounted on the engine cylinder andformed with an opening communicating with the exhaust port, said platehaving substantially parallel sides each having a lip bent over to makea narrow track, and a dished muflier cover formed with an outer wallspaced from the opening in the plate and obliquely arranged to deflectgases entering the mufller cover, and slots in said outer wall to permitthe gases to exhaust from the mufiler cover, said cover havingsubstantially parallel sides formed with narrow flanges to slip underthe lips on each side of the plate and fasten the cover thereto, wherebythe cover may be removed pro viding easy access to the exhaust port.

3. A muiiler for the exhaust port of an internal combustion enginecomprising a plate adapted to be mounted upon an internal combustionengine and having an exhaust inlet for communicating with said exhaustport, a dished cover being detacha'bly mounted upon said plate andhaving an outer wall equipped with an exhaust outlet, said outer wallbeing inclined away from said plate to define a tapered muflier chamberof increasing crosssectional area from said inlet to said outlet, saidplate having substantially parallel sides turned inwardly to providelips, said cover having substantially parallel sides formed with narrowflanges adapted to slip under the lips of the plate for slidably anddetachably securing the cover thereto, whereby, the cover may be easilyremoved to provide access to the exhaust port of the internal combustionengine.

References Cited in the file of this patent UNITED STATES PATENTS1,634,000 Smith June 28, 1927 2,675,662 Kroll Apr. 20, 1954 FOREIGNPATENTS 329,237 Great Britain May 15, 1930

